Process for the production of tertiary phosphine oxides

ABSTRACT

A PROCESS FOR THE PRODUCTION OF TERTIARY PHOSPHINE OXIDES WHICH COMPRISES CONTACTING A SUITABLE ARYLPHOSPHINE HALIDE WITH POWDERED SODIUM IN AN OXYGEN-FREE ATMOSPHERE AND THEREAFTER REACTING THE PRODUCT OF SAID REACTION WITH A SUITABLE HYDROCARBYL HALIDE IN AN OXYGENCONTAINING ATMOSPHERE.

3,751,482 PROCESS FOR THE PRODUCTION OF TERTEARY EHQSPHINE GXIDES KurtWeinberg, Upper Saddle River, NJ., assignor to Union CarbideCorporation, New York, N.Y. No Drawing. Filed Dec. 1, 1971, Ser. No.203,826 Int. Cl. C071? 9/02 US. Cl. 260-6065 P 10 Claims ABSTRACT F THEDISCLOSURE A process for the production of tertiary phosphine oxideswhich comprises contacting a suitable arylphosphine halide with powderedsodium in an oxygen-free atmosphere and thereafter reacting the productof said reaction with a suitable hydrocarbyl halide in anoxygencontaining atmosphere.

This invention relates to a process for the production of tertiaryphosphine oxides and more particularly to a process for the productionof tertiary arylphosphine oxides or mixed aryl alkyl phosphine oxides byreacting an arylphosphine halide with a hydrocarbyl halide and powderedsodium in an oxygen-containing environment.

The present invention provides a useful and economical process for theproduction of tertiary arylphosphine oxides and/or mixed tertiary arylalkyl phosphine oxides which comprises reacting a suitable arylphosphinehalide with powdered sodium to produce aryl phosphine sodium andthereafter reacting the aryl phosphine sodium with a hydrocarbyl halidesuch as an aryl or alkyl halide in an oxygen-containing environment.

The suitable aryl phosphine halides are those of the structure Ar -PXWhere Ar is aryl of 6 to 14 carbon atoms such as phenyl, o-tolyl,naphthyl, phenanthryl and anthracyl; X is halogen such as bromine andchlorine; n is 1 or 2.

Compositions according to the above include phenylphosphine dichloride,diphenylphosphine monochloride, l-naphthylphosphine bromide,chlorotolylphosphine chloride and dichlorotolylphosphine chloride.

The suitable hydrocarbyl halides are those of the structure RX Where Ris alkyl of 1 to 25 carbon atoms; aryl of 6 to 14 carbon atoms;arylalkyl or substituted arylalkyl of 7 to 16 carbon atoms, such asbenzyl and p-chlorobenzyl; alkaryl of 7 to 16 carbon atoms such aso-tolyl, p-tolyl and dimethylphenyl; and cycloalkyl of 3 to 15 carbonatoms such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl andcycloheptyl; X is as above defined.

The suitable arylphosphine halides can be obtained by the processdisclosed in my U.S. Pat. 3,557,204 issued Jan. 19, 1971 and assigned toUnion Carbide Corporation.

Briefly, there is disclosed therein a process for the production ofarylphosphine halides which comprises reacting an aryl halide with whitephosphorus in the pres ence of a catalytic amount of a Lewis acid. Thearyl halides that are employed can be represented by the formula RXwherein R represents an aryl radical or an alkaryl radical, preferably ahydrocarbon aryl or alkaryl radical, having from 6 up to 10 or morecarbon atoms and having a valence of m, wherein X represents a halogroup, preferably a bromo, chloro or iodo group, and wherein mrepresents a number having a value of from 1 to 3. Specific illustrativearyl halides include chlorobenzene, bromobenzene, iodobenzene,fiuorobenzene, p-dichlorobenzene, the trichlorobenzenes,o-chlorotoluene, m-chlorotoluene, 2,4-dichlorotoluene,l-chloronaphthalene, l-bromonaphthalene, the bromotoluenes, theiodotoluenes and l-iodonaphthalene.

"United States Patent 0 The catalysts that are employed in the abovepatented process include stannic tetrachloride, titanium tetrachloride,aluminum triiodide, ferric triiodide, aluminum trifluoride, ferrictrifluoride, ferric tribromide, and the like. The preferred catalystsinclude ferric trichloride, aluminum trichlon'de, aluminum tribromide,and ferric tribromide.

The proportions of the reactants employed in the above patented processare not narrowly critical. For example, the mol ratio of Whitephosphorus (PQcaryl halide can vary from about 1: /z to 1:60, preferablyfrom about 1:2 to 1:12, and more preferably from about 1:4 to about 1:6.The Lewis acid catalyst is employed in small catalytic quantities. Forexample, the catalyst can be employed in a proportion of from about 0.1weight to about 3 weight percent and preferably from about 0.2 weightpercent to about 1.5 weight percent, based upon the total weight of thereactants.

The process described in U.S. Pat. 3,557,204 is carried out at elevatedtemperatures. The exact temperature employed is dependent somewhat uponthe particular nature of the aryl halide reactant. For example, when anaryl chloride is the reactant, the operable temperature range isnormally from about 280 C. to about 420 C., preferably from about 300 C.to about 400 C. and more preferably from about 330 C. to about 360 C.When the aryl halide is an aryl bromide, the temperature which then canbe employed will normally be Within the range of from about 200 C. toabout 450 C., preferably within the range of from about 250 C. to about370 C., and more preferably from about 280 C. to about 300 C. When thearyl halide is an aryl iodide, the temperature range is preferablysomewhat below the temperatures indicated for aryl bromides, for examplepreferably from about 250 C. to about 290 C. When the aryl halide is anaryl fluoride, somewhat higher temperatures than those indicated foraryl chloride should preferably be employed. For example a preferredtemperature range when the aryl halide reactant is an aryl fluoride willbe from 400 C. to about 450 C.

For a more detailed description of the preparation of these startingmaterials, reference is made to the above mentioned patent.

Sodium is also employed as a reactant in the process of the presentinvention. It is critical to the successful practice of the process ofthe invention that the sodium be employed as fine particles averagingless than 3 millimeters in diameter and preferably less than 2millimeters in diameter and most preferably less than 1 millimeter indiameter. As a general rule, I have found that the speed of reaction isincreased in proportion to the decrease in size of the sodium particles.The powdered sodium can be prepared by introducing sodium (slices orpieces) into a hydrocarbon solvent having a boiling point at least equalor greater than the melting point of sodium. The mixture is then heatedto its boiling point at which time the sodium melts. The melted sodiumis then vigorously agitated with a suitable agitator such as a Hershbergstirrer, or alternatively, a vibrator may be employed. This technique iscontinued until the sodium is converted into a fine powder measuringabout 3 mm. or less diameter (average) particle size.

When the starting material is an aryl phosphine dihalide, at least 4moles of sodium are required per mol of aryl phosphine dihalide toconvert all of the aryl phosphine dihalide to the aryl phosphinedisodium. When the starting material is a diaryl phosphine monohalide,at least two mols of sodium are required per mol of diaryl phosphinemonohalide to convert all of the diaryl phosphine monohalide to thediaryl phosphine sodium. From this it can be seen that a stoichiometricamount of sodium is needed to convert the starting material to itssodium derivative; however, larger amounts can be employed if desired.

In general the reaction can be conducted at elevated temperatures suchas from about 50 C. to about 150 C., preferably from about 100 C. to 130C.

The reaction between the sodium and the aryl phosphine halide is carriedout for a period of time sufficient to produce the sodium arylphosphine.It has now been found that this reaction can be completed within aperiod of time of from about 1 to 6 hours.

After formation of the arylphosphine sodium (which appears on visualobservation as a yellow precipitate), the hydrocarbyl halide is added tothe formed arylphosphine sodium. The hydrocarbyl halide is graduallyadded to the vessel containing the arylphosphine sodium with agitationand if desired additional solvent can be added at this time. Theproportions of the reactants are also not narrowly critical except thattoo large an excess of hydrocarbyl halide would lead to quaterm'zationof the tertiary phosphine. In general therefore stoichiometric amountsof hydrocarbyl halide and arylphosphine sodium are required. An excessof the hydrocarbyl halide as much as 20 mol percent can be used ifdesired.

Since the reaction is generally exothermic, the addi tion should becarried out without heating.

The reaction products form immediately on addition. After completion ofthe addition, the reaction mixture is heated to reflux temperature tocomplete the reaction Since the reaction is exothermic it will, ofcourse, be understood that the reaction is conducted in a vesselequipped with cooling means which serve to control the extent of heatformation. The reaction between the hydrocarbyl halide and the sodiumarylphosphine is carried out for a period of time sufiicient to producethe desired products, such as from about 30 to 120 minutes. The exacttime, of course, will depend upon the nature of the reactants, thereaction temperature and the like.

In the reaction of the arylphosphine sodium with the hydrocarbyl halidethe reaction is conducted in an oxygen-containing atmosphere. Thus thereaction can 'be conducted in an open zone such as in an open vessel,that is, one in which the reactants are exposed to the atmosphere.

The products which can be produced according to the above generalreactions have the structure wherein Ar, R and n have the aboveindicated values. Merely as illustrative, the following products can beobtained according to the above general reactions: triphenylphosphineoxide, tri(1-naphthy1phosphine) oxide, tri(p-tolyl)phosphine oxide,hexyldiphenylphosphine oxide, dihexylphenylphosphine oxide,didecylphenylphosphine oxide and decyldiphenylphosphine oxide.

I have further found that in preparing the commercially importantcompound triphenylphosphine oxide, that this compound can be produced ina one step procedure by admixing the suitable reactants, e.g.,phenylphosphine dichloride and chlorobenzene together with the powderedsodium in a low boiling solvent such as diethylether and in anoxygen-free atmosphere and thereafter continuing the reaction byagitating the mixture in an oxygen-containing atmosphere at refluxtemperature.

The following examples illustrate the present invention.

EXAMPLE 1 Preparation of phenyldioctylphosphine oxide A solution of 35.8g. (.2 mol) of phenylphosphine dichloride in 30 ml. of xylene was addedto a stirred suspension of 20.2 g. (.88 gram-atom) of sodium powderhaving a particle size of less than 3 mm. in diameter, in

a dry oxygen-free atmosphere at 40-50 C. After the addition wascompleted the mixture was refluxed with stirring for an additional 6hours. During this time 1.5 ml. portions of dibutylether were added tothe reaction mixture every 60 minutes to accelerate the formation ofphenylphosphine disodium. The original grey mixture turned olive greenafter about 4 hours. The stirring and refluxing was continued foranother 2 hours. The mixture was then cooled to room temperature and asolution of 77.2 (.4 mol) of l-bromooctane in 60 m1. of xylene Was addedto the mixture with stirring over a period of 2 hours. After theaddition was completed the reaction mixture was refluxed in air for 15minutes and thereafter about 300 ml. of diethylether was added. 55 ml.of water was then added slowly to the mixture. The resulting layers wereseparated and the top layer was dried over magnesium sulfate anddistilled in vacuum. The phenyldioctylphosphine oxide distilled at2102l8 C./.9 mm. and melted at 39-42 C.

EXAMPLE 2 Preparation of phenyldihexylphosphine oxide A solution of 35.8g. (.2 mol) of phenylphosphine dichloride in 30 ml. of xylene was addedto a stirred suspension of 20.2 g. (.88 gram-atom) of sodium powderhavmg a particle size of less than 3 mm. in diameter, in a dryoxygen-free atmosphere at 40-50 C. After the addition was completed themixture was refluxed with stirring for an additional 6 hours. Duringthis time 1.5 ml. portions of dibutylether were added to the reactionmixture every 60 minutes to accelerate the formation of phenylphosphinedisodium. The original grey mixture turned olive green after about 4hours. The stirring and refluxing was continued for another 2 hours. Themixture was then cooled to room temperature and a solution of 66 g. (0.4mole) of n-hexyl bromide in 60 ml. of xylene was added to the mixturewith stirring over a period of 2 hours. After the addition was completedthe reaction mixture was refluxed in air for 15 minutes and thereafterabout 300 ml. of diethylether was added. 55 ml. of water was then addedslowly to the mixture. The resulting layers were separated and the toplayer was dried over magnesium sulfate and distilled in vacuum. Thephenyldihexylphosphine oxide distilled at -l73 C./.4 mm. and melted at58-60 C.

EXAMPLE 3 Preparation of phenyldidecylphosphine oxide A solution of 35.8 g. (.2 mol) of phenylphosphine dichloride in 30 ml. of xylene wasadded to a stirred suspension of 20.2 g. (.88 gram-atom) of sodiumpowder having a particle size of less than 3 mm. in diameter, in a dryoxygen-free atmosphere at 40-50 C. After the addition was completed themixture was refluxed with stirring for an additional 6 hours. Duringthis time 1.5 ml. portions of dibutylether were added to the reactionmixture every 60 minutes to accelerate the formation of phenylphosphinedisodium. The original grey mixture turned olive green after about 4hours. The stirring and refluxing was continued for another 2 hours. Themixture was then cooled to room temperature and a solution of 88.5 g.(.4 mol) of n-decyl bromide in 60 ml. of xylene was added to the mixturewith stirring over a period of 2 hours. After the addition was completedthe reaction mixture was refluxed in air for 15 minutes and thereafterabout 300 ml. of diethylether was added. 55 ml. of water was then addedslowly to the mixture. The resulting layers were separated and the toplayer was dried over magnesium sulfate and distilled in vacuum. Thephenyldidecylphosphine oxide distilled at 220/226 C./.33 mm. and had amelting point of 54-5 8 C.

EXAMPLE 4 Preparation of isopropyldiphenylphosphine oxide A solution of22.1 g. of diphenylphosphine chloride .1 mol) in 30 ml. of xylene wasadded slowly to a suspension of 6.1 g. of sodium powder (.265 gram-atom)having a particle size measuring less than 3 mm. diameter, in 60 ml. ofhot xylene under nitrogen. After completion of the addition, refluxingand stirring was continued for an additional one hundred minutes. 14.6g. of isopropylbromide in 25 ml. of butyl ether was then added and thereaction mixture, exposed to air and stirring continued for about 25minutes. The reaction mixture was then filtered and the solvent of thefiltrate evaporated. The isopropyldiphenylphosphine oxide yield was 79percent of theory.

EXAMPLE 5 Preparation of n-propyldiphenylphosphine oxide A solution of22.1 g. of diphenylphosphine chloride (.1 mol) in 30 m1. of xylene wasadded slowly to a suspension of 6.1 g. of sodium powder (.265 gram-atom)having a particle size measuring less than 3 mm. diameter, in 60 ml. ofhot xylene under nitrogen. After completion of the addition, refluxingand stirring was continued for an additional one hundred mintues. 14.6g. of n-propylbromide in 25 ml. of xylene was then added and thereaction mixture exposed to air and stirring continued for about 25minutes. The reaction mixture was then filtered and the solvent of thefiltrate evaporated. The n-propyldiphenylphosphine oxide yield was 81percent of theory.

EXAMPLE 6 Preparation of triphenylphosphine oxide room temperature. Theyield of triphenylphosphine oxide was 69 percent of the theoretical(based on phosphorus).

EXAMPLE 7 Preparation of triphenylphosphine oxide A mixture of 22.1 g.(.1 mol) of diphenylphosphine chloride and 13.7 g. (.12 mol) ofchlorobenzene in 80 ml. of diethylether is added to a suspension of 6 g.sodium powder (.26 gram-atom) in 60 ml. of diethylether. After stirringand refluxing the mixture in an oxygen-containing atmosphere for 3 hoursit was stirred at room temperature for 8 hours, filtered, and thesolvent in the filtrate slowly evaporated at room temperature. The yieldof the triphenylphosphine oxide was 92 percent of the theo retical(based on phosphorus).

Instead of using phenylphosphine dichloride and diphenylphosphinechloride separately as starting materials, a mixture of these tworeactants may be used and reacted with sodium and chlorobenzene in ananalogous manner.

Although the invention has been illustrated by the preceding examples,it is not to be construed as limited to the materials employed therein,but rather the invention encompasses the generic area as hereinbeforedisclosed. an

Various changes and modifications can be made in practicing the presentinvention without departing from it and, therefore, it is intended toinclude in the scope of the appended claims all such modifications andvariations as may be apparent to those skilled in the art from thedescription and illustrative examples given herein.

What is claimed is:

1. A process for the production of tertiary phosphine oxides whichcomprises contacting an arylphosphine halide having the formula whereinAr is aryl of 6 to 14 carbon atoms; X is halogen and n is 1 or 2, withpowdered sodium in an oxygen-free environment and thereafter reactingthe product of said reaction with a hydrocarbyl halide having theformula wherein R is an alkyl of 1 to 25 carbon atoms; aryl of 6 to 10carbon atoms; aralkyl of 7 to 16 carbon atoms; and cycloalkyl of 3 to 15carbon atoms; X is as above defined; in an oxygen-containing environmentat a temperature and for a period of time sufiicient to produce tertiaryphosphine oxides.

2. A process according to claim 1 wherein said powdered sodium has anaverage particle size of less than 3 mm. in diameter.

3. A process according to claim 2 wherein said arylphosphine halide isphenylphosphine dichloride.

4. A process according to claim 2 wherein said arylphosphine halide isdiphenylphosphine chloride.

5. A process according to claim 2 wherein said hydrocarbyl halide isn-octyl bromide.

6. A process according to claim 2 wherein said hydrocarbyl halide isn-hexyl bromide.

7. A process for the production of triphenylphosphine oxide whichcomprises contacting phenylphosphine dichloride with chlorobenzene inthe presence of powdered sodium having a particle size of less than 3mm. diameter, said reactants being admixed in an oxygen-free atmosphere,and thereafter continuing the reaction in an oxygen-containingatmosphere at a temperature and for a period of time sufiicient toproduce triphenylphosphine oxide.

8. A process according to claim 7 wherein diphenylphosphine chloride issubstituted for phenylphosphine dichloride.

9. The process of claim 1 wherein the oxygen-containing environment isair.

10. The process of claim 7 wherein the oxygen-containing atmosphere isair.

References Cited UNITED STATES PATENTS WERTEN F. W. BELLAMY, PrimaryExaminer

